Recently a behavioral model has been developed in rats in which one can measure separately short- and long-term memory for item or order information within the same task. The distinction between short- and long-term memory is indicated by a serial position curve for recognition of a list of items (arms in a radial arm maze). It has also been shown that within the same task, the hippocampal formation contributes to long-term memory (LTM) and the neocortex to short-term memory (STM). Based on the observation that in Alzheimer's disease there are specific neuroanatomical, specifically cholinergic changes, within the neocortex and the hippocampal formation with concomitant deficits in STM and LTM, we propose to use this animal model as a means to assess the neurobiological basis of Alzheimer's disease. Thus, the first two specific aims of the proposal are to determine whether the cholinergic system projecting to the neocortex via the basal forebrain and projecting to the hippocampal formation via the medial septum subserves STM and LTM, respectively. Based on the observation that elderly humans and senescent rats have dificits primarily on tasks requiring the operation of LTM, but have few impairments on tasks requiring primarily STM, it should be possible to assess whether the STM and LTM components of the behovioral model are sensitive to aging. Thus, the third specific aim is to measure age-related impairments in STM and LTM ability.